Caravan hookups

[Carlosfandango]

I was asked to test five caravan pitches for someone I've done a few jobs for. Now, I'll admit my knowledge on TT systems is not vast so I'm looking for a bit of advice. The install has been tested by a large local contractor every three years. When I got there the setup was as follows. BS 1361 cutout - meter- 63 amp 100mA rcd - 16mm Swa - 5 way db (63amp 30mA main switch) (roughly 20m away),then out to the hookups via 10 amp mcb's. There was a 10mm earth out to multiple rods connected to the RCD steel enclosure (as told by customer). There was also a 16mm earth to the PME cutout? I know this is incorrect so I disconnected it and got 110 ohms Ra. This is obviously classed as stable but not ideal. My problem is, why did this other contractor not pick up on this, or am I the one that's wrong?? Before anyone else pipes up I know there are other faults ie no overload protection on the supply to the 5 way db!
Thanks for reading!

 

[Guest77]

Regarding RCDs, I haven't really taken in what you have said about it yet here, best practice is RCDs at the caravan point rather than away from it IMO, however I will have another read of the OP later and respond again tommorrow, if I can get in before E54 LOL

 

[Guest77]

Thanks guys, I was doubting myself as I have the previous 15 years test sheets and there is no mention of any of the issues I found!

Well there should have been a code regarding the PME bit on the existing sheets, the inspector didn't know his oninions from his garlic I am afraid, at least you have questioned it, section 7 will have much more.

 

[Doomed]

As I say, TT'ed at the hook up, mixed at the source.
708.553.1.14 & 708.411.4

 

[Carlosfandango]

But it's not tt'd at the hookup, it tt and PME at source.

 

[Plonker 3]

But your are introducing the PME potential to the TT

 

[Guest77]

But it's not tt'd at the hookup, it tt and PME at source.

Thats no issue, I thought you meant mixing at the caravan outlet end, as it is now thats the case, thats why Carlos disconnected the PME earth due to the concern the outlets were PMEd, that is what the thread is basically about.

But your are introducing the PME potential to the TT

Quite right fella, thats why I suggested to carlos he connect the existing earth into a wago in the back of the outlet and rod at that point.

 

[Guest77]

But it's not tt'd at the hookup, it tt and PME at source.

Well then thats fine, the whole thing sounds confusing, but at the source fine, not the outlet. Can you clarify again lol

 

[Doomed]

and one final question - are you sure its PME and not TN-S?

 

[Carlosfandango]

Wait, I'm confusing things here! I explained it better in my first post!! I think?

 

[Carlosfandango]

Definitely pme, not tn-s.

 

[Engineer54]

I was asked to test five caravan pitches for someone I've done a few jobs for. Now, I'll admit my knowledge on TT systems is not vast so I'm looking for a bit of advice. The install has been tested by a large local contractor every three years. When I got there the setup was as follows. BS 1361 cutout - meter- 63 amp 100mA rcd - 16mm Swa - 5 way db (63amp 30mA main switch) (roughly 20m away),then out to the hookups via 10 amp mcb's. There was a 10mm earth out to multiple rods connected to the RCD steel enclosure (as told by customer). There was also a 16mm earth to the PME cutout? I know this is incorrect so I disconnected it and got 110 ohms Ra. This is obviously classed as stable but not ideal. My problem is, why did this other contractor not pick up on this, or am I the one that's wrong?? Before anyone else pipes up I know there are other faults ie no overload protection on the supply to the 5 way db!
Thanks for reading!

There is no problem connecting a TT system to any TN supply earthing, although an Ra value of over a 100 ohms isn't going to add anything to a PME system!! From what i can tell from the OP, you are saying that the SWA radials away from the 5 way DB are carrying the same PME supply earth to the caravan hook-ups, which is also fine.

It's at the caravan hook up's where the PME earthing system needs to be isolated from the caravan plug and socket supply , and a TT system earth provided.... The caravan plug & socket hook up points should contain the 30mA DP RCD's not at the 5 way DB as has been stated. That 30mA main switch in the 5 way DB should be changed out for a straight isolator, and the RCD after the meter changed out for a 100 or 300mA S type. Whats the betting the CU in the caravan is also protected by a 30mA RCD too lol!

 

[driverman]

Caravans parks should be tested every year not 3 years as stated by OP. Is it a residential site as opposed to a touring site? PME is acceptable on the distribution side. TT can be created at the hook up's to the caravans.

 

[driverman]

May be true,maybe not., but I heard on the grapevine, that when the new regs come out there will be major changes re caravan site installations. Anyone know anything?

 

[Jamzie]

Statics every 3 years, tourers every year. That's what it used to be, but I've been away from the game for a few years-has it now changed?

 

[Leesparkykent]

professional-electrician.com/.../niceic-advicesupplies-pme-system-caravan-...